Radio battery eliminator



Aug. 28, 1928. 1,682,492

P. E. EDELMAN- I v RADIO BATTERY ELIMINATOR ,Filed May 17, 1927 INVENTOR.

Patented Aug. 28, 1928.

UNITED STATES PHILIP E. EDELMAN, OI CHICAGO, ILLINOIS.

namo BATTERY ELIMINATOR.

Application filed May 17,

.My invention relates to radio power supply and similar devices in which alternating current is converted to direct flowing current,

filtered and supplied to a load circuit such -as a connected radio receiving set without employing any battery. An object of my present invention is to provide a reliable bate tery elminator capable of supplying direct current to standard radio sets of varying types and sizes despite various current reuirements thereofwhich will'function satisactorily notwithstanding Variations in the applied alternating current line voltage, and

controllable from the regular radio set switch. Various other objects will presently appear.

I illustrate an embodiment of my invention a in the accompanying drawing in which Figure 1 is a schematic diagram of my battery eliminator circuit, Figure 2'is a diagram of a suitable construction for the transformer 6 of Figure 1, Figure 3 is a diagram of a suitable assembly for the choke coils 40, 43 of Figure 1, and Figure 4. is a front elevation partly sectioned showing a suitable rectifier holder 26 of Figure 1.

i I aim in my invention to provide an efiicient battery eliminator economlcal on current consumption and using no alternating 'current while the connected radio set is not in use. I also aim to completely suppress disturbances of radio frequency nature occurring in the alternating current line or in the rectifier circuit, so that same will not have detrimental effect on the connected radio set. I also pro vide effective and novel filtering means to suppress low frequency fluctuations from the output of the-device.

Referringnow more particularly to Figure 1, a standard socket plug 1 is provided for attachment to a 110 volt alternating current lighting main socket-outlet in usual manner. This connects via contact switch 3 of relay 5 to supply current to primary winding 7 of transformer 6 as wellas to provide a live power outlet 2 foruse'in driving any B power unit attached thereto. The relay switch contact 3 is normally open so that no current flows from plug 1 therethrough. Since thereis no battery in my device and no current used when the output terminals 45, 46 are not supplying a load, a manually operated push 4 is provided to start the current thru contact 3, after which relay 5 immediately pulls and retains contact 3 closed as 1:127, Serial mi. 192,010.

long as terminals 45, 46 are supplying a load. However when the circuit from output termlnals 45, 46 is opened relay 5 is no longer energized sufliciently to hold switch contact 3 closed, so it automatically opens, thus restoring the device to condition of open circuit drawing no current from socket connection 1. Spring 65 does this.

After much experimentation I find that the transformer 6 is best constructed with its primary winding 7 and secondary winding 8, 9, 10 placed side by side on the core 36, so as to reduce the capacity 12 inherent in between these two windings which otherwise facilitates radio frequency line disturbances. Thus a circuit exactly as shown using ordinary type of transformer winding in which this provision is not made, such as a primary and secondary wound over each other, may make the circuit impractical due to radiofrequency energy transfer between such windings without such provision. 1 This undesired action manifests itself as a crackling sound in the loud speaker ofthe connected radio set and is entirely due to radio frequency disturbances in the rectifier circuit connected to transformer 6. The employing of such special winding substantially suppresses undesired transfer of radio frequency disturbances between the primary coil 7 and second-" ary winding 8, 9, 10. An extra tap 11 may be provided on the primary coil 7 to accommodate other primary voltage input than the .rated 110 volts for which same is designed.

In case the radio frequency disturbances are not completely suppressed by the trans.- former construction as may be due in certain localities to noisy transmission lines on which sparking disturbances occur, I may use a neutralizing condenser 13 of about microfarad capacity connected between the primary coil 7 and the terminal 20 of secondary coil 8, 9, 10, as indicated by switch 14.

A suitable size for transformer 6 comprises an E type core on which the primary and secondary coils aforesaid are wound slde by side. This core may be by 1%" cross I section with winding space 3 Ion The primary may comprise 660 turns of o. 24 enamelled magnet wire. The secondary may com prise No. 18 magnet wire wound with turns for coil portion 8, 65 turns for coil portion 9 and 9 turns for coil portion 10. Small by-pass condensers 15, 16 preferably connect between the junction of windings 8 and 9 the connection via wire 32 is 0 en circuited by removing cap connector 30 rom the terminal 29 of rectifier 28, only the other similar rectifier connected by wire 33 via cap connector 31 fitting over its terminal 29 is effective, and half wave rectification is obtained. In the latter case terminal pin 21 may be moved from contact jack 19 to contact jack 20 in order to obtain higher output at "-Qminal 19 for balanced rectification.

terminals 45, 46 when only one rectifier cartridge 28 is so employed. When both similar rectifier cartridges 28, 28 are employed, the pin connector 21 must be moved to jack ter- Since the transformer 6 has 35 watt rating it can supply either half wave or full wave operation as set forth without changing the secondary coils 8, 9, 10 thereof other than by said switching means.

While any suitable type of rectifier nfay be employed in my eliminator I illustrate the use of cartridge rectifiers 28 of the colloidal silver type described by M. Henri Andre (Communication faite a la S. A. T. S. F., seance du mercredi 12 decembre 1925, LOnde Electrique January 1926) as marketed in the United States under the trade name of Raytheon A rectifier. Such reetifier cartridges are very efficient electrically but notoriously unsuited to filter circuits heretofore known in this art due to the radio fre uency disturbances they cause, as descri d in the above French publication. I have therefore been obliged to make the following improvements to secure practical use,

of such rectifier csirtridges-firstly the provision set forth to suppress the effect of radio fre uency disturbances otherwise manifested as isagreeable crackling noises in the loud speaker of the connected radio set; secondly providing for improved contact means 26,

30 and 27, 31 respectively for each cartridge 28, 28 used to avoid microphonic contacts which manifest their effect as fluctuations insupply at terminals 45, 46 due to the extremely low internal resistance of rectifiers 28, 28. Thus the clip contacts recommended by the makers of such rectifiers 28 while suitable for a battery charging circuit in which fluctuations are permissible, are not suitable for use in a rear battery eliminator circuit employing no battery,'1n which fluctuations arenot tolerable. Thirdly, I have found it necessary to provide special heat cooling means in the cartridge holders 26, 27 to keep the operating temperature below 120 degrees F. in order to obtain satisfactory life endurance of the cartridges 28, 28 in service. The reasons only set forth herein will be more evident from a study of the French publication cited.

The cartridges 28 comprise a sealed cell of the silver-colloidal silver-nickel type in which an oriented conductivity conjunction is maintained at the surface between said colloidal silverand nickel element. While the cut off is efficient on reversal of current, it is subject to radio frequency disturbance which I have discovered to be due to minute sparking inside the cartridge in the colloidal silver mass, as may be observed by partially cutting open an operating cartridge 28. The thermic: radiation holders 26, 27 should be constructed to dissipate four to five watts each. thereby minimizim the occurrence of said minute sparks in the cartridge 28 held thereby. Such holders as I provide increase the operating life of the cartridge 28 by about 20%. The rectifier outputs are labelled plus and minus. In service the rectifiers 28 never heat so much that they feel uncomfortably hot if touched by ones hand, and the measured reading on a thermometer is usually well under 120 degrees F.

. Coming now to the filter circuit, the rectifier output first feeds a large dry solid type condenser 37 constructed as set forth in'iny copending application for Letters Patent of the United States Serial No. 190,148. filed May 9, 1927, preferably with a capacity of the order of several thousand microfarads. The connections to this condenser 37 should be directly from the positive output from rectifiers 28. thence tonegative terminal 18 as shown. .Wire 24 also leads directly from positive rectifier output wires 32, 33 to the coil 40 of choke eoil 41. crably' enclosed in an iron conduit 25. Coil 40 is preferably located sufficient distance from transformer 6 to avoid direct magnetic linkage with core 36 thereof.

Coil 40 is comprised byNo. 15 enamelled magnet wire wound with 250 turns on a laminated core 41 of transformer sheet having an air gap 52. IfE type,the core cross section may be 1" by 1 with air gap of .013 inch at one end, in whichcase a winding length of 3 inches is suitablefor coil 40, affording a coil having considerably less than ohm direct current resistance. Coil 40 connects to positive terminal of condenser 38 and also to relay coil 5. Condenser 38 may"- be constructed similarly .to condenser 37 and returns directly to negative terminal 18 -as shown. This first section filters out the main fluctuations transferred by wire 24 and suf-' fices for use withmany sets without further filtering. However perfection of loud speak- Wire 24 is pref- 1 core with distributed air gaps has the peculiar ers and radio amplifiers of modern design makes the special filter addition comprised by coil 43 and condenser 39 necessary for quality results. Condenser 39 is constructed similarly to condenser 37 as described in my copending patent application aforesaid, and

has its positive terminal directly connected to output terminal while its negative return goes direct to output terminal 46. Wire 22 enclosed in iron shield 23 connects terminal 46 and negative terminal 18.

The'action of relay 5 has already been described. It should include wire 54 twisted together to avoid inductive current pickup as shown and not have more than th ohm direct current resistance. A suitable winding comprised by 150 turns of No. 18 enamelled magnet wire wound on a soft iron core may be used. Choke coil 43 may be constructed similarly to choke coil 40 but preferably will have only 200 turns of wire affording less resistance to direct flowing electric current, also greater air gap preferably attained by interposing a plurality of distributed gaps 42 along the core. Such a property which is very desirable of causing coil 43 to have an increased efl'ective' impedance to alternately fluctuating current as the amount of said current is increased, whereas coils with iron cores having small concentrated air gaps become less effective as .the current flow increases. The effect of coil43 therefore in part balances the effect of coil 40 with varying loads. .A further novel and desirable filtering action is had by mutually coupling with a small percentage of coupling indicated by arrows 44, the two coils- 40 and 43 whereby any slight residual fluctuating ficial effect critical onvarying load currents acurrent flowing in coil 43 will tend to be substantially counterbalanced by the oppositely phased induced current set up therein by reason of the small coupling 44 so placed. This may be determined experimentally for a given design of coils 40 and 43 and is not.

critical to duplicate as long as the selected dimensions are duplicated. Nor is this benepassing thru thecoils 40 and 43. The combination of opposed mutual inductance of the separated coils 40,43 is effective also despite some variation in frequency of current supplied to plug 1. Thecircuit so far described will supply satisfactory direct current substantially free from ripples to terminals 45 and 46. When automatic regulation of current with varying load requirements is wanted, switch 66 may be opened to throw small closed core impedance coil 17 in circuit. Coil 17 may comprise 40 turns of No.

. 15 enamelled magnet wire wound on an iron core 1 in cross section and 2 inches long, E type. Such a coil so connected in the rectifier circuit has the peculiar property of tending to partially regulate the rectifier output,

and tends to regulate the terminal voltage at terminals 45, 46 according to the load current drawn therefrom.

It is advantageous to locate relay coil 5 sufficiently distant from core 36 of transformer 70 6 so as not to pick up magnetic leakage .therefrom. Direct current suitable for operating radio sets equipped with storage battery type vacuum tubes may be had from terminals 45, 46. When radio sets requiring lower voltage 7 such as sets using vacuum tubes intended for dry cell operation are to be connected to ter f minals 45, 46, I provide an adapter 48 of about 9 ohms direct current resistance so that its terminals 47 and 49 connect to terminals line voltages as long as supply plugged into by plug 1 is suitable for satisfactory illumination purposes. Transformer 6 and circuit I thru. coils 17, 40, 43 provide a certain amount of self regulatlon even when varying line voltages are employed at plug connector 1. Output current at terminals 45, 46 when one rectifier 28 only is used as connected by wire 33 when pin 21 is in jack 20, rated maximum 6 volts direct current at 1% amperes When adapter 48 is used, terminals 50, 51 will afford ampere at 4 volts.

Output current when both rectifiers 28, 28 are employed with pin connector 21 in jack 19, maximum 2 amperes at 6 volts direct current, at terminals 45, 46, current consump- .1

tion at plug 1, 30 watts.

In case abnormally low line voltage must be used for operating plug 1, the use of both rectifiers 28 will permit satisfactory operation of most standard radio sets even when the line voltage supplied to plug 1 is under 100 volts.

The eliminator set thereby, with reference Having now described a suitable embodiment of my invention it is obvious that various changes and modifications may be made within the scope of the appended claims. Before setting forth the details of'Figures 2, 3, and 4 it'm'ay be remarked here that in the 5 practical working'of myeliminator I have observed a peculiar effect which may be due to piezo-electric action in the condensers 37 38, 39.. This is more-particularly noticed under certain conditions in condenser 37, due to the solid crystal q struction employed therein as set forth inx mgi co-pending patent applications S. No. 190,148 filed May 9, 1927, and S.

No. 163,734 filed Jan. 26, 1927. When the I eliminator unit of Figure 1 is in service'a definite mechanical vibration corresponding show substantially no residual ripple therefrom in the output at terminals 45, 46. Although piezo electric action has been employed in radio circuits (see U. S. Patent 1,- 450,246 for example) 'I believethat the use thereof in filtering-circuits is new and described for the first time in this specification. The condenser 37 for example is comprised by two aluminum sheets 7 inches wide and 8 ,feet long interwound With blotter paper as spacers therefor, while the whole-is impregnated with a chemical salt mixtureelectrically formed during the crystallization thereof, so that a substantially rock like masscomposition comprises condenser 37. The mass of interlinked crystals comprised in condenser 37 thus appears to have a certain advan tageous piezo-electric property which in part accounts for the eflicient filtering action obtained. I have observed the various behaving types of condensers constructed of equal surface material in both flat plate and convolution shapes and have conceived that the selection of a volume selected at least partially tuned to or resonant with theapplied alternating or rectified current frequency or harmonics thereof is beneficial, so when plug. 1 is connected to a sixty cycle supply it is advantageous to select dimensions for condenser 37 which are at least approximately capable of vibration response at similar frequency or harmonic thereof. Experimental means for determining crystal resonance are suggested by A. Meissner in the Proceedings of the Institute of Radio Engineers, April 1927, page 282, Figure 2. Or, as in my laboratory work, results may be determined from readings on an oscillograph machine, selecting the particular dimensions which afford minimum residual ripple. in the practical operating circuit set forth. Thus in my device of Figure 1 I have observed that larger sized condensers than the indicated kind afford no advantages, proving that very approximately correct dimension for eflicient result as set forth is thereby provided. Such a piezoelectric element proportioned for a particular low frequency reasonance will also be effective on the first harmonic of said frequency.

The means provided to mitigate the effect of radio frequency disturbances include firstlyf the transformer windings made with minimized electrostatic coupling between primary and secondary coils as set forth, secondly absorbing shunt condensers of small size 15, 16, thirdly the shielded conductors sential to use short direct Wiring between the parts. The wire 24 in particular must not be looped around the apparatus parts or lengthened so that it can act as a radio frequency loop transmitter. The various parts shown are preferably encased in an iron sheet metal box as is customary in this art. Suitable wire for said wiring is comprised by No. 16 flexible insulated copper conductor.

A transformer-made as shown by Figure 2 can have the primary coil 7 spaced adjacent to the secondary windings 8, 9, 10 by a spacer 55 of metal or fibre to further reduce the radio frequency coupling therebetween.

A suitable means to obtain the desired mutual coupling counteracting effect in the choke coils 40, 43 of Figure 1 is indicated in Figure 3. Coil 40 has a core 41 with its. air

gap portion 52 placed as shown at the remote end away from core 56. Core 56 comprised with coil 43 has a plurality of distributed air gaps 42 as indicated. A screw 61 cooperating with threaded support 60 permits the angle between core 56 and core 41 to be adjusted correctly for best result. Band supports 57, 59 hold the two assembled choke coils 40, 43 in fixed relation determined by this adjustment 61, 60. This latter adjustment can be fixed for a given set of coil'dimensions.

In Figure 4 the rectifiercartridge is indicated by 28, and also has a terminal 29. The

body of cartridge 28 can be placed down in the special holder 26 while contact is made to terminal 29 by the cap connector 30 to which flexible wire 32 is fastened, at projection terminal 65 thereof. A slot 64 is provided in cap 30'only to facilitate removable and insertion of cap 30 on contact terminal 29 with a tight contact thereon.

Holder 26 is provided with a series of air cooling vanes or ribs 63 and also a plurality of slots 62. The ribbed vanes 63 are made to rapidly conduct heat away from the lower portion of cartridge 28. The slots 62 are to afford a springy contact surface between holder 26 and cartridge 28. Only the bottom portion of cartridge 28 need be so provided with thermic cooler 26 as the active portion of cartridge 28 is at the bottom end thereof. Holder 26 as well as cap 30 can conveniently be made in this manner as screw machine products. The construction set forth by way of example has the surprising effect of increasing the life of cartridge 28 by causing same to operate at lowered temperature with reduced internal electric stresses at the instant reversed current is arrested therein.

'at low frequency for which same is proportioned.

2. In a radio battery eliminator, a filter circuit including a condenser having piezoelectric properties approximately dimensioned to assist in suppression of undesired low frequency current ripples.

3. In a radio battery eliminator, a filter circuit including two choke coils having sep arate cores so placed that the mutual coupling between said coils causes ripple current flowing in one of said coils to be substantially opposed by electroniagneticall y induced ripple current supplied by the other of said two coils, and a by-pass condenser connected at the junction of said two coils.

4. In a radio battery eliminator, a filter circuit comprised by two choke coils one of which has a core with relatively small air gap while the other has a separate core including a plurality of distributed air gaps therein, a by-pass condenser connected to the junction of said two coils, means to couple said two coils with a low percentage of mutual coupling suflicient to induce some ripple current from one of said coils into the other to oppose the flow of residual ripple current flowing in said other coil.

v 5. In a radio battery eliminator theimprovement which conslsts in a filter circuit employing a condenser having piezo-electric properties proportioned to absorb ripple cur-- rent flowing in said filter circuit at approximately the frequency of. the line current applied to operate said eliminator and the first harmonic of said frequency.

6. In a radio battery eliminator the improvement which comprises a filter circuit including a condenser constructed with piezoelectric pro erty proportioned to absorb some of the ripp e current flowing thru said filter circuit.

7. In a radio battery eliminator the improvement which comprises a filter circuit having a condenser therein including a crystalline mass with piezo-electric propertyapproximately proportioned to absorb some of the ripple current flowing in said filter circuit 8. As a radio battery eliminator, in' combination, a transformer, a rectifier operated therefrom, a filter circuit supplied with energy via said rectifier, a condenser in said filter circuit constructed with piezo-electric property approximately dimensioned to absorb some of the ripple current flowing in said filter circuit, a switch to control current supply to said transformer, an electromagnet in said filter circuit to hold said switch closed while load current flows in said filter circuit, means to open said switch when no load current flows thru said filter circuit, and auxiliary means combined with said transformer and filter circuit to suppress radio frequency currents from the output of said filter circuit.

In witness whereof I have hereunto'set my hand this 10th day of May, 1927.

PHILIP E. EDELMAN. 

